1. Field of the Invention
The present invention relates in general to a tamper-evident closure and neck structure for containers. The closure is substantially applied to the container neck with an axial downward force and removed by unscrewing the closure from the neck. The closure includes a tear skirt which ruptures when the closure is initially removed from the container neck to provide visible evidence that the container has been opened.
2. Description of the Related Art
The snap-on, screw-off structures available in the prior art are of two general types--those having thread engagement as initially applied, and those without initial thread engagement. The no-thread initial engagement system has the major advantages of being simple to manufacture and apply and achieving good re-seal on reclosure through the thread torque. However, using a lined closure with this system is somewhat difficult and the consumer may be confused by the requirement of twisting the closure relative to the neck after the container is initially opened by a lifting motion. Examples of closure systems having no-thread initial engagement are those taught by U.S. Pat. No. 4,561,553 to Crisci, and U.S. Pat. No. 4,946,055 to Towns et al.
Systems having partial to full thread engagement after the initial application have several advantages over the no-thread system, including the elimination of consumer confusion. However, the initial thread engagement systems often do not offer the manufacturing and application advantages available with the no-thread-engagement system. With some closure systems, capping equipment which twists the closure relative to the neck must be used at some point during the application process. An example of such a closure is shown in U.S. Pat. No. 4,625,875 to Carr. Other concepts, such as that taught by Miskin in the European Patent Specification No. 0 118 267 do not require orientation or twisting during application, and accommodate for the inevitable closure height variation after application by employing an extended plug to seal against the inside bore of the container neck.
Both the system taught by Carr and Miskin suffer from the requirement that the tamper evidencing band must be expanded over a restrictive container bead during the application process. This requirement leads to application difficulties, especially in the Miskin concept where the rotary assist as taught by Carr is not employed. An additional problem common to both the Carr and Miskin concepts is that the lower tamper evidencing band is joined to the upper closure skirt through bridges requiring mold slides for formation, a feature which greatly increases the cost and complexity of injection molding tooling. Finally, in both the Miskin and Carr concepts the tamper evidencing band remains on the bottle after initial opening, a feature which thwarts effective container recycling.
GB Application No. 2,114,553 to Guala shows an example of a system which is similar to Carr and Miskin. The closure includes a security band formed with axial notches which are adapted receive one of the projections on the exterior of the neck. The closure is applied by pushing the closure onto the neck, with the security band expanding outwardly to pass over the projections on the neck. Unless the cap is perfectly aligned with the neck, the projections will not seat in the notches, requiring the cap be rotated relative to the neck. The Guala closure also must be manufactured using a split mold, increasing the costs and complexity of the tooling.
Other systems available in the art include screw-on, screw-off structures which also offer the advantages of initial thread engagement and elimination of consumer confusion. An example of this type of closure is shown in U.S. Pat. No. 3,980,195 to Fillmore. The system taught by Fillmore includes a threaded, tamper-evidencing closure with a removable band. The interior of the removable band is formed with a one-way ratchet, which cooperates with projections formed on the neck to prevent unscrewing of the container. When the closure is initially twisted onto the neck, the ratchet teeth slip over the projections on the neck. The band must be removed prior to opening the container.
The snap-on, screw-off structures have several advantages not found with the closure taught by Fillmore. The application process used with the screw-on, screw-off systems is quite complex, since the cap must be turned or rotated relative to the container until the closure is fully seated. The frangible connections between the tamper-evidencing band and the closure must be sufficiently strong to prevent partial separation when the cap is twisted onto the container. However, manufacturing variations can result in excessive strength of the frangible connections and the consumer will often have difficulty removing the closure, since the band must first be separated from the rest of the cap.
This invention provides a snap-on, screw off system with partial or full thread initial engagement by reason of a unique thread design and a unique tamper-evidencing band. The present invention offers considerable advantages over prior structures as is evident from the description of the related art and the following description of the invention.